(1) Field of the Invention
The field of the invention is viewgraph projectors and in particular image projection using fiber-optic bundles.
(2) Description of the Prior Art
Viewgraph projectors are typically configured with a light source and mirror assembly contained in a projection box. The light source leaves the projection box vertically upward through a glass window on which a transparency is located. The image generated is directed upward to a focusing lens and mirror assembly held in position by an extension arm. This assembly turns the projection beam horizontally and directs a focused image onto a display screen. Because of the glass top on the projection box, natural convective cooling is impeded. Additionally, the location of the transparency above the light source on the glass surface has a stove top effect. As a result, the projection box requires a large and noisy cooling fan and other electrical and structural parts.
The changing of viewgraph transparencies requires the speaker to be located at the projector box. The design thereby places the projector, the extended arm, the focusing lens and mirror assembly, and the speaker himself, all in the direct line of viewing of the audience, creating a major obstruction to viewing, and, because of the cooling fan, creating a major impediment to hearing.
Work around methods, such as using a second seated operator to change viewgraphs, are undesirable since they limit the speaker's use of pointers or other direct control of the viewgraphs. Additionally, the structure of the projector itself remains in the direct line of view of the audience.
In order to move the projector and speaker out of the line of view of the audience, it is necessary to provide a means of transmitting the projected images from a side-located projector to the required projection point. It is well known in the art that optical images may be transmitted by fiber-optic bundles. Commercially available coherent bundles are now suitable for image projection.